Bubble cap for washing gases and vapors



June 17, 1952 y' y||. N. WADE 2,600,710 BUBPLL cAP FOR WASHING GASES ANDvAPoRs Filed Nov. 15, 1947 HENRY N WADE /NVE/vron A TTORNEV Patented`une 17, 1952 UNITED STATES TENT OFFiiE BUBBLE CAP FOR WASHING GASES ANDVAPORS Henry N. Wade, Los Angeles, Calif.

Application November 15, 1947, Serial No. 'l86,l75

(Cl. Ztl-114) 2 Claims. 1

This invention relates generally to a method of and devices forintimately contacting liquids with gases or vapors, and specically toimproved forms of bubble caps for use in vapor fractionating columns.

A purpose of the invention is to ensure that the liquid collecting onthe fractionating plate is contacted once only with vapor before passingto the plate next below.

A purpose of the invention is to provide means for ensuring that thequantitative relation between liquid and vapor passing through each ofthe bubble caps on any one plate is substantially uniform.

A purpose of the invention is to avoid the bypassing andshort-circuiting of vapor and/or of liquid which may occur in the use ofother forms of bubble cap when the plates on which they are mounted areimperfectly levelled.

A purpose of the invention is to avoid the inequality in degree oftreatment on different parts of a plate which follows from extendedhorizontal flow of liquid over the plate.

These and other advantages will be evident on inspection of the attacheddrawings and the following description thereof, in which Fig. 1illustrates in internal elevation a form of the bubble cap in which thecontacted liquid is collected in a centrally disposed basin providedwith a central downcomer;

Fig. 2 illustrates, in the same manner, a slightly modified form of thebubble cap in which the liquid-collecting receptacle and associateddowncomers are disposed around the periphery of the cap proper;

Fig. 3 is a diagram, on a much reduced scale, suggesting a suitablearrangement on the plate of the form of cap shown in Fig. 1, and

Fig. 4 is a similar diagram suggesting an arrangement on the plate ofthe form of cap shown in Fig. 2.

Referring first to Fig. 1. lil is a fragment of a plate extending fromwall to wall of a fractionating column, scrubber or absorber. A vaporuptake Il extends above the plate for a sufcient distance to maintain apool of liquid of a desired depth on the plate when the apparatus is outof operation and preferably, but not necessarily, extends also to aslight distance below the plate. i

The vapor uptake is surrounded by a sleeve l2 which is slotted orperforated along its lower edge in any conventional manner, as at I3. Ata level somewhat below the upper edge of this sleeve a ring I4 isinserted, this ring carrying a dependent downcomer i5, the ring anddowncomer preventing upward flow of vapor and directing it throughperforations i3. The downcomer seals in liquid on the plate next below,as is illustrated by the fragmental tubes Iii-I6 which represents thedowncomers from. two caps on the plate next above and which extend belowthe surface of liquid pool Il. The extension of sleeve l2 above ring I4forms a relatively shallow catchment basin for contacted liquid. thisliquid draining through downcomer l5.

Around sleeve I2 and preferably concentric therewith is placed aneduction shield I8 so supported above the upper face of plate It (by anymeans not shown) as to allow a free flow of liquid beneath its loweredge. The upper end of this ring-shaped shield may be open but I preferto close it partially, as by I neans of a hat ring i9 having a centralopening 20.

The functioning of this device is illustrated by the solid lines 2|-2lshowing, in a generalized manner, the directions of gas flow, and by thebroken lines 22-22 showing the general directions of liquid flow.

Gas or vapor, as the case may be, flows upwardly through uptake Il,encounters ring I4 and is directed downwardly through the annular spacebetween sleeves ll and l2 and outwardly through slots or perforationsI3. Assuming a sufficient depth of liquid on the plate to submerge theupper ends of the slots, the upward flow of vapor through the annulusbetween sleeves i2 and I8 entrains a iiow of liquid which is ejectedfrom the upper end of the annulus. At low vapor velocities the liquidwill merely well up and overflow; at higher velocities it will beejected in the form of a spray. In either case the mixture of vapor andliquid is retarded in the enlarged space above the annulus, the liquidfalls into catchment basin 23 and is delivered through downcomer l5 ontothe plate next below, and the vapor passes through opening 2i into thevapor space below the plate next above.

The limit of capacity of the cap is reached at the point at which thevapor-liquid spray is ejected so forcibly that the liquid is unable toseparate from the vapor within the confines of the cap, it beingessential to the best functioning of the device that only an immaterialproportion of the liquid be carried over into the vapor space and thusreturned to the pool on the plate from which it was withdrawn. The ringIB in the upper end or the cap acts as a baffle and assists inseparating and returning liquid to the collecting basin and is highlydesirable where the vapor 3 velocity is high, though it may be omittedif the caps are to operate at low vapor velocities.

In the form shown in Fig. 2 a sleeve 24 is concentrically arrangedaround sleeve I3 and the annulus thus formed is closed at the bottom bya ring 25, forming an annular catchment well 26. This well is drained byone or more downcovers 21 which seal in liquid on the plate next below.The central downcomer I5 may be omitted, substituting a disc I4' for thering I4 of Fig. 1, or, if desired, it may be retained to affordadditional drainage. It is preferable to omit it from the form of Fig. 2to fperrnit the caps to be placed closer together.

The form of Fig. 2 functions inaexactly the manner above described, theonly difference between the two forms being in the location of thecollecting receptacle and downcomers. `The second form allows somewhatmore room above the electing annulus for the separation of liquid fromvapor and will tolerate a higher vapor velocity through theperforations. On -theother hand, this separating space is "gained 'atthe expense of a greaterv cap diameter, allowing a smaller number orcaps on a plate of given diameter.

As the contact between liquid and vapor isproduced solely within the'connes' of "the cap, no exterior space 'for the bubbling of vap'or'through liquid is required. vIn consequence, vthe 'caps may be veryclosely spaced on the plate, even lface to face as illustrated in Figs.3 and 4. l

In these figures, the solid 'circles i8 and 24`indicate the positions ofthe caps n'o'ne' plate and the dotted circles I8 and 24 the relativepositions of the caps on the plates'immediately above 'and below. 1nFig. 3 the downcomer l5 (of Fig. 1) is centered in the free spacebounded by four adjacent caps. In Fig. 4 this space receives thedowncomers 21 of two adjacent "caps" of 'the'type shown in Fig. 2. Thesefigures suggest 'merely a minimum spacing and the caps may in 'practicebe distributed over the plate'in any preferred pattern. Y y Y Columnsequipped with these bubble caps have several advantages over columnsofthe conventional form in which the vapor is bubbled through a pool ofliquid and in which Vthe liquid flows from one sideof the plate totheother before passing to the plate next below. n

For example, in the conventional column vthe resistance to vapor flowthrough any 'one cap 'is a function of the depth to which the slots orperforations are submerged. It follows that'if any plate departs fromlevel by tilting, sagging or buckling, the higher lying caps will'pass avgreater amount of vapor through a shallower layer of liquid than thoselying at a lowerlevel,

and the vapor will be unequally treated'over different areas of theplate. In extreme cases the caps on the higher part of the plate maylose submergence and permit vapor to blow through, or those lying atlower levels may drown out and permit no vapor to pass, or permit liquidto "now down through the vapor uptake.

Even though the plates be maintained level,

-the flow of liquid across the plate requires a material hydraulic headand in columns of' relatively great diameter, which are now coming-intocommon use, the difference in depth of liquid between the two sides of aplate may be enough'to cause a material difference in effectivenessbetween caps in different plate areas.

In the use of the form of bubble cap above described, the resistance tovapor nowls xedby the pressure drop through the perforations or slotsand by the height of the contacting annulus 3| and is largelyindependent of the depth of liquid surrounding the cap. As these factorsare uniform for all the caps on a given plate, and as the quantity ofliquid entering the contacting annulus is determined by the quantitywhich the vgas now is able to eject (assuming sufficient free spacebelow shield I8) the liquid flowthrough the annulus is atleastsubstantially independent Vof the depth of liquid surrounding the cap.Thus vit is impossible for a cap to unload or blow vdoing the liquidlissuccessiv'ely 4contactedwith several streams of vapor from acommon'source and of identical composition. The *maximum differencein'composition between the liq'uid and the Vapor exists only at thepointfatwhich `the rst contact is effected and decreasesas the'contactsare repeated, only the lrstcap in the line of flowfunctioningatthemaximum efciency.

In the use'of Ythe bubble caps of 4the'present invention this'difficulty isv entirely avoided; rst by providing each bubble 'c'ap withat i leasty one down'comer, thus' bringing Ithe down'c'omers so closethat horizontal flow is reduced to' 'an immaterial distance,` second,'by contacting liquid and vapor Vin a confined 'space"in"'which liquidand'vapor are again' 'separated and from" which the once treated liquid'is withdrawn onto 'the next lower plate without returning to 'theliquid pool from Which'the 'untreated liquidwas drawn. In thecooperation of these "two provisions, difficulties due to imperfectliquid distribution entirely disappear and ythe liquidiowingfrom oneplate to the next 'may be equally contacted over the entire area of 'theplate.

An important 'advantage in "the 'described structure is thepossibilityofmaking the contacting annulus'l rslong'as may be "desired,permitting the time of contact to be Iextended and the intimacy ofContact to' beincreased to any 'extent desired. With Yeven a moderatedepth of laimulus and a"'moderate 'vapor velocity, the contact producedis "much more intimate and effective than 'that produced 'by 'the freebubbling of streams ofva'por' through a pool of liquid.

While the drawings Ishow the caps as'consisting of cylindricalelementsthey' maybe formed with straight sides 'in 'any'desired relative"dimensions, Vso V`long as the walls"l2 vand I8 are kept parallel andthe contacting annulusil "of uniform width. `No advantage `is'presentlyseen `the capsin a` column' m'ay'bev 'expected to'p'er- 'fo'rm'in thesame manner, a determination of the capacity and the optimum proportionsfor a single cap permits a column to be designed for the bestperformance without the elaborate balancing of numerous variablesotherwise required.

I claim as my invention:

1. In a gas-liquid contacting column having a plate, a contacting unitcomprising: a gas uptake extending above said plate; an inverted cupsurmounting said uptake and provided along its lower edge with means fordividing a gas stream into a plurality of minor streams; a ringshapedshield surrounding said inverted cup and spaced therefrom to form arelatively narrow, vertical, annular conduit having parallel walls, thelower edge of said shield being spaced from said plate to allow liquidfrom said pool to enter said annular conduit; means disposed within saidshield for collecting liquid educted through said annular conduit, saidcollecting f means arranged to prevent return of the educted liquid tothe pool from which it was withdrawn, and means for draining saidcollected liquid onto a lower-lying plate, said last means arranged toprevent overow of liquid from said pool and to receive only saidcollected liquid.

2. A contacting unit adapted to be mounted on a horizontal partitionplate in a gas-liquid contacting column and to maintain a liquid poolthereon, said unit comprising: a gas riser extending above the surfaceof said plate; a cup inverted over said gas riser and provided along itslower edge with means for dividing a stream of gas into a plurality ofminor streams; a tubular shield surrounding said cup and formingtherewith a relatively narrow, vertical, annular conduit havingsubstantially parallel walls, the lower end of said shield being spacedfrom said plate to allow liquid to enter said conduit from said pool andto be ejected therefrom by said gas streams; means disposed within saidshield for collecting the liquid so ejected, said means being arrangedto prevent said liquid :from returning to the pool from which it wasdrawn, and a tube passing through said plate and sealed in liquid on alower-lying plate for draining said collecting means without permittingthe overflow of liquid from said pool.

HENRY N. WADE..

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,651,354 Alexander Dec. 6, 19271,725,052 Braun Aug. 20, 1929 1,744,543 Grace Jan. 21, 1930 1,748,595Chillas, Jr. et al. Feb. 25, 1930 1,808,088 Urquhart June 2, 19311,821,619 Day Sept. 1, 1931 1,899,409 Bottoms Feb. 28, 1933 1,948,500Bielfeldt Feb. 27, 1934 1,981,346 De Florez Nov. 20, 1934 1,983,762Kotzebue Dec. 11, 1934 2,042,150 Hagenbuch May 26, 1936 2,150,498 Geddeset al Mar. 14, 1939 2,345,667 Hachmuth Apr. 4, 1944 2,497,136 PattersonFeb. 14, 1950

